The present invention relates to body electrodes of the type applied to the trunk and limbs of patients in connection with surgical, therapeutic and diagnostic procedures using electromedical instruments. Dispersive electrodes are used to complete electrical circuits at the point of body contact with such instruments in order to distribute current density over a larger area. Dispersion of electrical current over increased area minimizes tissue heating problems which may result in skin necrosis.
Dispersive body electrodes typically include an electrically conductive inner portion having a surface area of several square inches, an electrically insulating cover sheet overlying the inner portion, and an adhesive securing the cover sheet to the skin. An electrically conductive gel is usually applied to the skin to optimize electrical contact with the conductive inner portion. The cover sheet is a stretchable, resilient sheet of a foam plastic material which must be stretched to force the conductive inner portion into parallel relationship with the skin surface and to force out residual air pockets.
Problems may arise with such body electrodes if medical personnel stretch the cover sheet either too little or too far. When an electrode sheet is stretched to its optimal degree, the conductive inner portion is generally parallel to the skin surface so that electrical capacitance and current distribution are substantially uniform. When the cover sheet is stretched too little, the conductive inner portion and skin surface are likely to become nonparallel, thereby producing hot spots in areas of increased capacitance and residual air pockets or gaps in other areas. When the cover sheet is stretched too far, excessive tension on the cover sheet tends to peel it away from adhesion with the body surface.